Configuring the 4th axis in NX
| Setting | Example |
|---|---|
| Machine type | 4-axis with rotary table (or head) |
| Rotary plane / axis | A about X (VMC) or B about Y (HMC) |
| Limits | Continuous, or e.g. -360 to +360 |
| Direction | Shortest path or signed direction |
| Resolution | 0.001° |
| Rotary feed mode | Inverse time or degrees per minute |
HMC B-axis indexing
(HMC - index pallet, then machine face)
G91 G28 Z0.
M11 (unclamp B - machine specific)
G90 G00 B90.
M10 (clamp B - machine specific)
G54 X0. Y0.
G43 H03 Z100.On HMCs, each face often uses its own work offset or a rotating work offset; the post follows the shop's chosen method.
Variable-axis 4-axis toolpaths
For continuous 4-axis operations, the post outputs simultaneous XYZA (or XYZB) motion and handles feedrate correctly, typically via inverse time (G93) or a controller-specific rotary feed method.
Tcl customisation examples
- Automatically insert clamp/unclamp around rotary moves.
- Reset the rotary axis to within 0–360° between operations.
- Output comments with the face or angle being machined.
A 4-axis post that clamps, indexes and unwinds correctly saves both cycle time and bearings.
NX 4-axis posts
See our CNC post processor development service and HMC post development.